The present invention relates to a method for wrapping or packaging bales in strips of plastic packaging film, in which the bale is rotated about a generally horizontal axis and, when appropriate, also about a generally vertical axis, and in which packaging film is taken from a film magazine located at a distance from the bale and wrapped in successive turns around the entire bale while maintaining a tension force in the film, and in which the film in each turn extends essentially parallel with and transversely to the horizontal axis.
The invention also relates to an arrangement for carrying out the method, and to bales.
Methods and arrangements of the aforesaid kind are known essentially. One large area of use is found in the wrapping of bales of animal fodder, ensilage, which is still not dry and which is to be wrapped in an air-impervious plastic film wrapping. Present-day bales have an essentially circular cross-section, i.e. they are not parallelepipedic.
The known technique, however, is encumbered with serious drawbacks. In order for ensilage to be wrapped in the manner intended, it is necessary for the wrapped bale to be truly airtight. Even though the film wrapper is maintained under considerable tension as it is wound, it is extremely difficult to achieve the requisite tension in the wrapper and requisite retention of the wrapping material around the bale, particularly on those parts of respective turns which are parallel with horizontal axis. At times, the joints produced with the aid of glue applied to the side of the film which faces towards the bale are insufficiently strong, therewith allowing moisture and air to enter the bale material. This ingress of air and moisture will destroy the bale material, due to mould growth among other things. Toxic substances are also likely to form. When moisture is present, the adhesive force exerted by the glue will diminish progressively, thereby quickly worsening the situation. The problem is, of course, still greater in the absence of glue joints. One contributory factor to the described moisture susceptibility with insufficient retention of the wrapping turns is that the joints on one of the turn-parts parallel with the horizontal axis of each turn opens upwardly and is therefore susceptible to rain, etc. On the other of these two parts of the turn, however, the joints are downwardly open, i.e. a certain "roof tile effect" is obtained.
When practicing the known technique, it cannot be guaranteed that a uniform and high bale material quality will be achieved.
The problems of poor wrapper tension and poor wrapper retention increase when passing from cylindrical bales to generally parallelepipedic bales, this transition being desirable for storage and transportation reasons, among other things. This worsening of the problem is mainly because the sides of a parallelepipedic bale are mutually parallel and because when wrapped, the bale has a certain dog-leg configuration, which further impairs the situation.